Deleting Time Machine backup files

I need some advice from the Time Machine experts out there. I made the mistake of going into Time Machine and deleting the oldest backup files myself by moving to Trash.. (instead of letting Time Machine manage it's self by deleting the oldest files when the disk is full).

Now, I can't Empty Trash when Time Machine is plugged in:
"The operation cant be completed because an unexpected error occurred (error code -8003)."

And Time Machine can no longer backup, it doesn't delete files automatically to make space anymore and this error message pops up:
"This backup is too large for the backup disk. The backup requires 81.12 GB but only 76.78 GB are available.".

All of those previous backup files are stuck in the Trash and can't be deleted to make space for new backups.

Surely you have backups for those "other files" on another volume, don't you? If not, can't you make copies of those files on your internal HD now? If not, you gambled, and it seems you lost.

You will need to erase that entire external HD that your TM backup files are on now, complete with the "other files", if you want to regain control of it. Sometimes shit happens.

So what you're saying is if I copy all the "other files" I want to keep from the external onto the internal HD, wipe the external HD using Disk Utilities and set it back as "Backup disk for Time Machine", all will return to normal?

If so, great, many thanks for the advice,
only thing, is there a way I can retrieve any of the old backup files from the Trash when TM is plugged in? I would ideally like to hang onto at least one several moth old backup file if possible.

is there a way I can retrieve any of the old backup files from the Trash when TM is plugged in? I would ideally like to hang onto at least one several moth old backup file if possible.

Perhaps you can retrieve them with special software. However, Time Machine is an incremental backup system. Which means that any subsequent, incremental, backup file only records what changed relative to the first and earlier backups. I.o.w.: all TM's backup files of one set together will work as a system. So just one or two of those incremental files aren't complete backups! Because the rest of the set is absent.

Copy everything you want to hold on to, to your internal HD (or another external one). Erase the external HD and set it up afresh as the destination for TM. Set TM to work at making the first, complete backup. And copy those special files back from your internal HD to the newly erased external HD.

Perhaps you can retrieve them with special software. However, Time Machine is an incremental backup system. Which means that any subsequent, incremental, backup file only records what changed relative to the first and earlier backups. I.o.w.: all TM's backup files of one set together will work as a system. So just one or two of those incremental files aren't complete backups! Because the rest of the set is absent.

Copy everything you want to hold on to, to your internal HD (or another external one). Erase the external HD and set it up afresh as the destination for TM. Set TM to work at making the first, complete backup. And copy those special files back from your internal HD to the newly erased external HD.

Thanks Rokcet Scientist, very well explained and thanks for the advice. I have retrieved the files i wanted, wiped the external hard drive, reset it as backup for TM, all is now working soundly.

i also tried to delete many time machine back up folders at once. the trash spent all night trying and it never worked. just do a bout 7 folders at once. works fast. if you want to first put all the folders you want to delete in another folder on time machine so you can quickly find the 7 to delete from it with out getting confused or lost. i made a folder in time machine titled "to trash". then put all the unwanted folders in it, then dragged 7 at a time to the trash. deleted trash and repeated. i read that once the external HD is full that time machine will make room for new files. maybe try that before. one more tip. i decided not to delete all old back up folders and to just keep one folder from every three months. just in case.

To delete all backups of one or more items from a Time Machine backup, follow these steps:

Click the Time Machine icon on your Dock to enter the Time Machine restore interface.
Click on the item you would like to delete. Command-click to select multiple items.
Control-click (or right click) the highlighted item(s) and select "Delete All Backups of..." from the contextual menu, or select "Delete all backups of..." from the Action Item menu.
Authenticate with an administrator password when prompted.